1. Field of the Invention
The present invention relates to a recording apparatus for recording an image to a recording medium and having an optical type detecting means within this recording apparatus.
2. Related Background Art
FIG. 6 is a perspective view showing the schematic construction of a conventional recording apparatus.
In FIG. 6, reference numeral 101 designates an ink tank of each color. Each ink tank is exchangeably mounted to a carriage 102. A recording head (not shown) for recording or printing an image to a recording medium (not shown)is arranged in the carriage 102. The image is recorded to the recording medium in accordance with a recording signal transmitted from an unillustrated substrate through an unillustrated flexible cable. Plural patterns showing information corresponding to a shifting amount of a printing position are printed to the recording medium by the recording head so as to relatively align the printing position at a first printing time to the recording medium with a printing position at a second printing time.
The recording apparatus shown in FIG. 6 is a so-called serial type printer. The carriage 102 is guided and supported so as to freely reciprocate in the direction of an arrow A along a guide shaft (not shown) arranged in a chassis 108. The carriage 102 is operated and controlled in position and movement by a driving mechanism such as a carriage motor (not shown), a motor pulley (not shown), a driven pulley 106, a timing belt 107, etc.
The recording medium such as a sheet of recording paper, etc. is fed by a paper feeder 110 until a nipping position of a conveying roller 111 and a pinch roller 113 within a body of the recording apparatus. The pinch roller 113 is held by a pinch roller holder 112. The pinch roller holder 112 is held by a pinch roller holder attaching plate 109 fastened and fixed to the chassis 108 by vises, etc. The pinch roller 113 comes in press contact with the conveying roller 111 by a pressing member such as a spring, etc. The recording medium conveyed to the above nipping position is further conveyed by the conveying roller 111 rotated by a driving mechanism (not shown).
Reference numeral 130 designates an optical type sensor of a reflection type as an optical detecting means mounted to the carriage 102. The optical type sensor 130 detects a printing pattern of the recording medium conveyed onto a platen 114 by scanning the carriage 102 in the direction of the arrow A. The optical type sensor 130 has a light emitting portion and a light receiving portion. Light emitted from the light emitting portion is reflected on a surface of the recording medium and the reflected light is detected by the light receiving portion.
A density of the pattern is detected by utilizing that intensity of the reflected light is changed in accordance with the density of the pattern printed on the recording medium.
However, in the prior art explained above, a problem exists in that external light enters the interior of the recording apparatus and no optical type sensor is normally operated in a certain case.
FIG. 7 is a cross-sectional view showing a conveying path of the recording medium in the conventional recording apparatus shown in FIG. 6.
In FIG. 7, reference numeral 116 designates the recording medium and shows a state in which the recording medium 116 is conveyed by the paper feeder 110. Reference numeral 115 designates a paper feed plate for guiding the recording medium 116 conveyed by the paper feeder 110 until the conveying roller 111.
Since the recording medium 116 stacked in the paper feeder 110 is arranged outside the recording apparatus body, the recording medium 116 is exposed to external light 117. Further, since the recording medium 116 is normally formed by a white color system, the external light 117 is well reflected on the recording medium 116. Accordingly, as shown in FIG. 7, the external light 117 is guided into the recording apparatus by the recording medium 116.
Further, since no member for pressing the recording medium 116 is arranged between the pinch roller holder 112 and the paper feed plate 115, there is a case in which the recording medium 116 is floated upward as shown by a dotted line in FIG. 7. In recent years, a high accuracy of about .+-.10 .mu.m is also required in conveyance of the recording medium. However, when the recording medium is floated upward as mentioned above, a conveying position is correspondingly shifted so that conveying accuracy is reduced.
FIG. 8 is a perspective view showing a conveying path of the recording medium shown in FIG. 7.
As shown in FIG. 8, plural pinch roller holders 112 are arranged in parallel with each other in a transversal one line in the conventional recording apparatus. However, since there is a clearance B between the respective pinch roller holders 112, the external light 117 is leaked from this clearance B and further enters the platen 114 (see FIGS. 6 and 7).
As mentioned above, the optical type sensor 130 detects the density of the pattern by intensity of the reflected light from the pattern printed on the reflected light from the pattern printed on the recording medium 116 conveyed onto the platen 114. However, when the external light 117 further enters the recording medium 116 on the platen 114, no reflected light of the optical type sensor 130 can be exactly detected by an influence of this external light 117 so that no density of the pattern can be exactly detected.